🌱 Plant Nutrition

🌞 Photosynthesis

Photosynthesis is the process by which green plants manufacture glucose from carbon dioxide and water, using light energy absorbed by chlorophyll. 🌿 Oxygen is produced as a by-product. This process occurs in the leaves and can be summarized by the following:

Word Equation: Carbon dioxide + Water → Glucose + Oxygen 🌍💧➡️🍬 + 🌬️

Chemical Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

🛠️ Products of Photosynthesis

• Used for respiration 🫁
• Converted to cellulose for cell walls 🏗️
• Combined with nitrogen to form amino acids 🍃💪
• Converted to sucrose for transport 🚚🍬
• Converted to fats and oils 🥑💧
• Converted to nucleic acids 🧬
• Excess glucose stored as starch 🥔

💡 Light and Dark Reactions

☀️ Light Reaction

Light energy splits water molecules into oxygen and hydrogen. 🌊➡️🌬️ Oxygen diffuses out, and hydrogen moves to the dark reaction stage.

🌑 Dark Reaction

Hydrogen from the light reaction combines with carbon dioxide to form glucose. 🍃💧➡️🍬

🔍 Testing for Starch in Leaves

• Boil the leaf in water to kill the protoplasm and make it permeable to iodine solution. 🔥💧
• Boil in alcohol to remove chlorophyll. 🍃🧪
• Add iodine to test for starch. Blue-black indicates starch; yellow-brown indicates absence. 🟦🟡

✅ Requirements for Photosynthesis

Essential factors for photosynthesis:

• Carbon dioxide: Enters through stomata. 🌬️➡️🌱
• Water: Absorbed by roots and transported through xylem vessels. 💧➡️🌳
• Sunlight: Provides energy. ☀️
• Chlorophyll: Captures light energy, converting it to chemical energy. 🌿⚡

🔬 Experiments to Demonstrate Requirements for Photosynthesis

🌬️ Carbon Dioxide Requirement

Destarch a potted plant by keeping it in the dark, then test exposed and non-exposed leaves for starch. 🌱🌑

💡 Light Requirement

Test exposed parts of a leaf for starch presence. 🌿🔍

📏 Measuring Photosynthesis Rate

Count oxygen bubbles from aquatic plants to measure the rate. 💧💨

🌿 Leaf Structure

🔍 External Structure

The leaf's design is optimal for photosynthesis, featuring:

• Thin lamina for light penetration 🌞
• Large surface area for maximum light capture 🌅
• Stomata for gas exchange 🌬️

🏗️ Internal Structure

• Palisade Cells: Contain the most chloroplasts for light absorption. 🌿
• Spongy Cells: Allow movement of gases and contain chloroplasts. 🌬️
• Veins: Carry water (via xylem) and photosynthetic products (via phloem). 🚰

🌍 Importance of Photosynthesis

• Food Production: Provides food for nearly all organisms. 🍽️
• Gas Balance: Helps maintain oxygen and carbon dioxide levels in the atmosphere. 🌬️🌍
• Energy Storage: Biomass produced can form wood, peat, and fossil fuels. 🌳🔥

🏡 Applications of Photosynthesis in Greenhouses

Greenhouses use transparent walls to retain heat and light, promoting optimal plant growth. Factors like artificial lighting and CO₂ enrichment make them more productive than open land farming. 🌞🏠

🌱 Plant Storage Organs

Plants store food primarily as starch and oils in modified structures such as:

• Root tubers: Swollen roots, e.g., sweet potatoes. 🍠
• Stem tubers: Swollen stems, e.g., potatoes. 🥔
• Bulbs: Fleshy leaves, e.g., onions. 🧅
• Rhizomes: Horizontal stems, e.g., ginger. 🌱
• Corms: Short vertical stems, e.g., Crocus. 🌷
• Seeds: Store nutrients for embryo development. 🌱

🧪 Mineral Nutrition in Plants

🔬 Major Elements (NPK)

• Nitrogen (N): Absorbed as nitrate or ammonium ions, crucial for protein synthesis. Deficiency causes stunted growth and yellow leaves. 🌱⚠️
• Phosphorus (P): Absorbed as phosphate ions, essential for nucleic acids and ATP production. Deficiency leads to purple leaves and poor root growth. 🍇⚠️
• Potassium (K): Vital for flowering, fruit formation, and ion transport. Deficiency leads to poor flowering and fruiting. 🌸🍏⚠️

🔍 Minor Elements

Magnesium: Part of chlorophyll, and its deficiency causes chlorosis (yellowing of leaves). 🌿⚠️

☣️ Effects of Sulfur Dioxide Pollution on Plant Nutrition

Sulfur dioxide, mainly from industrial emissions, forms acid rain, which can negatively impact plants by:

• Damaging the leaf’s waxy cuticle, increasing transpiration and potential leaf death. 🌧️🍃⚠️
• Injuring root hairs, thus reducing water and nutrient absorption. 🌱💧⚠️